Apparatus, system and method of operating an additive manufacturing nozzle

ABSTRACT

Apparatuses, systems and methods of providing heat to enable an FDM additive manufacturing nozzle having refined print control and enhanced printing speed. The heating element may include at least one sheath sized to fittedly engage around an outer circumference of the FDM printer nozzle; at least one wire coil at least partially contacting an inner diameter of the sheath; and at least one energy receiver associated with the at least one wire coil.

BACKGROUND Field of the Disclosure

The present disclosure relates to additive manufacturing, and, morespecifically, to an apparatus, system and method of operating a fuseddeposition of material (FDM) nozzle for additive manufacturing.

Description of the Background

Additive manufacturing, including three dimensional (3D) printing, hasconstituted a very significant advance in the development of not onlyprinting technologies, but also of product research and developmentcapabilities, prototyping capabilities, and experimental capabilities,by way of example. Of available additive manufacturing (collectively “3Dprinting”) technologies, fused deposition of material (“FDM”) printingis one of the most significant types of 3D printing that has beendeveloped.

FDM is an additive manufacturing technology that allows for the creationof 3D elements on a layer-by-layer basis, starting with the base, orbottom, layer of a printed element and printing to the top, or last,layer by heating and extruding thermoplastic filaments into thesuccessive layers. To achieve these results, an FDM system includes atleast a print head from which the thermoplastic print filament is fed toa FDM printer nozzle, an X-Y planar control form moving the print headin the X-Y plane, and a print platform upon which the base is printedand which moves in the Z-axis as successive layers are printed.

The FDM printer nozzle heats the thermoplastic print filament receivedfrom the print head to a semi-liquid state, and deposits the semi-liquidthermoplastic in variably sized beads along the X-Y planar extrusionpath plan provided for the building of each successive layer of theelement. The printed bead/trace size may vary based on the part, oraspect of the part, that is being printed. Further, if structuralsupport for an aspect of a part is needed, the trace printed by the FDMprinter may include removable material to act as a sort of scaffoldingto support the aspect of the part for which support is needed.Accordingly, FDM may be used to build simple or complex geometries forexperimental or functional parts, such as for use in prototyping, lowvolume production, manufacturing aids, and the like in a fraction of thetime it would take to manufacture such object using conventionalmethods.

However, the use of FDM in broader applications, such as medium to highvolume production, is severely limited due to a number of factorsaffecting FDM, and in particular affecting the printing speed, quality,and efficiency for the FDM process. As referenced, in FDM printing it istypical that a thermoplastic filament is heated to a molten state andthen squeezed outwardly from the FDM printing nozzle onto either a printplate/platform or a previous layer of the part being produced. The FDMprinter nozzle is moved about by the robotic X-Y planar adjustment ofthe print head in accordance with a pre-entered geometry, such as may beentered into a processor to control FDM printing head movements to formthe part desired.

Because of the advances in robotics and high available processing speed,the “choke point” for the FDM printing process is generally the FDMprinter nozzle itself. In particular, control over the speed of heatingand cooling of the FDM printer nozzle, and in particular refinements inthe control and start/stop timing of printing provided by advancedcontrol of heating and cooling of the nozzle, would allow forsignificant improvements in the printing provided by FDM technologies,but are not presently contemplated in the known art. Accordingly, theability to provide refined control and sensing of various aspectsassociated with FDM printing, such as heating and cooling of the printmaterial, pressure on and liquid state of the print material, and thelike, would allow for refinement of and improvement to the FDM process.

Notwithstanding the foregoing, currently available nozzles, for the mostpart, are metallic, and thus conductive, in nature, and have associatedtherewith a large heating block (such as may include a thermocouple forheating of the nozzle associated therewith) with a significant thermalmass. Thus, because of the large thermal mass of the heating block,refined control of heating and cooling of the nozzle is currentlylimited due to the permeation of heat to undesired aspects of themetallic nozzle. In addition, current nozzle designs make it difficultto focus heat to areas of the nozzle because of the typically conductivenature of the nozzle, and the slowness of heating and cooling of thenozzle caused by the large thermal mass of the heating block associatedwith the nozzle from which the control for the heating (and cooling) isprovided.

Accordingly, current nozzle designs suffer from significant issues whichimpede the ability to improve the FDM printing process. A principal oneof these impediments is the inability to provide refined control ofheating and cooling on the printing nozzle or on particular aspectsthereof. Lack of heating and cooling control may cause, for example,inconsistent melting of the thermoplastic material which may lead to lowprint speeds and nozzle clogging. Lack of cooling control may causeblobs, nipples or mis-printing to occur due to inability to quickly andaccurately control the temperature of the nozzle.

Therefore, the need exists for an apparatus, system, and method forproviding an FDM additive manufacturing nozzle having refined printcontrol and enhanced printing speed.

SUMMARY

The disclosed exemplary apparatuses, systems and methods provide atleast heat delivery to enable an FDM printer nozzle for additivemanufacturing having refined print control and enhanced printing speed.A heating delivery element may include at least one sheath sized tofittedly engage around an outer circumference of the FDM printer nozzle;at least one wire coil at least partially contacting an inner diameterof the sheath; and at least one energy receiver associated with the atleast one wire coil to increase the efficiency of the FDM printernozzle.

The disclosed exemplary apparatuses, systems and methods mayadditionally include the at least one wire coil comprising a nichromewire. Further, the at least one wire coil may comprise at least two wirecoils. The at least two wire coils may be at least partially staggeredalong a longitudinal axis of the FDM printing nozzle. The at least twowire coils may be respectively embedded in at least two sheaths. The atleast two sheaths may be concentrically about one another.

Thus, the disclosed embodiments provide an apparatus, system, and methodfor providing an FDM printer nozzle for additive manufacturing havingrefined temperature control, print control and enhanced printing speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed non-limiting embodiments are discussed in relation to thedrawings appended hereto and forming part hereof, wherein like numeralsindicate like elements, and in which:

FIG. 1 is an exemplary FDM print system;

FIG. 2 is an exemplary FDM print system;

FIG. 3 is an exemplary resistive nozzle hot end;

FIG. 4A illustrates a prior art FDM printer nozzle and associatedheating block;

FIG. 4B illustrates an exemplary resistive hot end printer nozzle;

FIG. 5 illustrates an exemplary delivery of power to a resistive hot endprinter nozzle;

FIG. 6 illustrates an exemplary FDM hot end printer nozzle;

FIG. 7 illustrates an exemplary hot end printer nozzle with an embeddedsensor; and

FIG. 8 illustrates an exemplary hot end printer nozzle with staggeredheating zones.

DETAILED DESCRIPTION

The figures and descriptions provided herein may have been simplified toillustrate aspects that are relevant for a clear understanding of theherein described apparatuses, systems, and methods, while eliminating,for the purpose of clarity, other aspects that may be found in typicalsimilar devices, systems, and methods. Those of ordinary skill may thusrecognize that other elements and/or operations may be desirable and/ornecessary to implement the devices, systems, and methods describedherein. But because such elements and operations are known in the art,and because they do not facilitate a better understanding of the presentdisclosure, for the sake of brevity a discussion of such elements andoperations may not be provided herein. However, the present disclosureis deemed to nevertheless include all such elements, variations, andmodifications to the described aspects that would be known to those ofordinary skill in the art.

Embodiments are provided throughout so that this disclosure issufficiently thorough and fully conveys the scope of the disclosedembodiments to those who are skilled in the art. Numerous specificdetails are set forth, such as examples of specific components, devices,and methods, to provide a thorough understanding of embodiments of thepresent disclosure. Nevertheless, it will be apparent to those skilledin the art that certain specific disclosed details need not be employed,and that embodiments may be embodied in different forms. As such, theembodiments should not be construed to limit the scope of thedisclosure. As referenced above, in some embodiments, well-knownprocesses, well-known device structures, and well-known technologies maynot be described in detail.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. For example, asused herein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The steps, processes, and operations described herein are notto be construed as necessarily requiring their respective performance inthe particular order discussed or illustrated, unless specificallyidentified as a preferred or required order of performance. It is alsoto be understood that additional or alternative steps may be employed,in place of or in conjunction with the disclosed aspects.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present, unless clearlyindicated otherwise. In contrast, when an element is referred to asbeing “directly on,” “directly engaged to”, “directly connected to” or“directly coupled to” another element or layer, there may be nointervening elements or layers present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.). Further, as used herein the term “and/or” includes anyand all combinations of one or more of the associated listed items.

Yet further, although the terms first, second, third, etc. may be usedherein to describe various elements, components, regions, layers and/orsections, these elements, components, regions, layers and/or sectionsshould not be limited by these terms. These terms may be only used todistinguish one element, component, region, layer or section fromanother element, component, region, layer or section. Terms such as“first,” “second,” and other numerical terms when used herein do notimply a sequence or order unless clearly indicated by the context. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of the embodiments.

Aspects of the embodiments may provide real time localization, controland targeting of nozzle heating, such as FDM nozzle heating, such as tocreate improved print control to allow for higher print speed andgreater print accuracy. These and other distinct advantages may beprovided in accordance with the provided improvements over the knownart, such advantages including lower nozzle costs and print costs;provision of the print nozzle as a consumable/disposable good;suitability for nozzle production using known semi-conductor and foundrytechnologies; enhanced design freedom for internal and external nozzlefeatures; and extremely fine control of hot and cold zones for both thenozzle and the printed material.

The disclosed improved printing apparatus, system, and method may beapplied to any type of 3D printing, such as FDM printing that usesthermoplastics, polymers, metals, ceramics, food, and wax printing, byway of non-limiting examples as the print material. More particularly,additive manufacturing can occur via any of various known methods,including the aforementioned FDM printing. By way of example, sinteringof powders may be performed in order to additively build layers.Further, for example, resin-based additive printing may be performed.

With regard particularly to FDM printing, current methods are generallyfairly slow and inefficient for additive manufacturing, and arepresently limited in the number of materials that may be printed. Thisis in large measure due to the inadequacies of known devices, systemsand methods for heating the printer nozzle in FDM systems. Heatingelements for additive manufacturing in the disclosed embodiments andequivalents thereto may rectify these inadequacies of known FDM systems.The disclosed heating elements may include, by way of non-limitingexample, resistive heating elements, an inductive heating element (suchas around the nozzle proximate to the orifice of the nozzle), anIR/radiative element, a RF coupled element, and so on.

More particularly, although the disclosed exemplary embodiments may heatand push material for “3D,” such as FDM, printing as is known in theart, they also provide refined heating and refined pushing of thatmaterial, such as through improved localization of heating. Heating ofthe print material in an FDM process is the single most important factorin refining FDM printing, and while fast printing is desirable toenhance available FDM printing processes, faster printing speeds requireincreased heating, and increased heating leads to less refined controlover the heating area for known nozzles, such as the presently availablemetal nozzles that are used in conjunction with large heating blocks.These known heating blocks and nozzles, in combination, also presentextreme difficulties in providing the expedient cooling necessary tostop printing, particularly in highly heat-conductive metal nozzles,which expedient cooling is necessary for refined heating control toallow for high-speed FDM printing.

In short, the high speed, high quality FDM printing provided in certainof the embodiments requires the transfer of as much controllable energyto the print material as is possible, at the greatest mass flow rate, tothereby allow for the desired increased printing speeds. Accordingly,the refined heating systems and methodologies disclosed herein improveprint speed and control in FDM printers. For example, the embodimentsmay provide at least inductive or resistive coil heating, such may beprovided by a coil wrapped about the nozzle using wet winding and/orsemiconductor fabrication processes, and such as may be wrapped on adielectric, metal, ceramic, or glass nozzle, and/or on a substrate layerapplied to nozzle, by way of non-limiting example.

That is, aspects of the disclosed embodiments may be employed on anonconductive or a conductive, such as a metal, nozzle. For example,dielectric layer(s), such as glass, may be deposited, such as via vacuumdeposition, CVD, PVD, or sputtering, onto a metal nozzle, therebyproviding an intermediate dielectric substrate onto which conductivelayers and/or coils may be placed.

The disclosed systems and methods may, in addition to the foregoingadvantages of refined heating, provide other heretofore unknownadvantages. For example, the disclosed embodiments and equivalentsthereto may help to prevent nozzle clogging. More specifically, one ofthe main dynamics that promotes clogging in the known art is that atraditional nozzle must be run at a significant temperature-rise overthe melting point of the thermoplastic. Once the print material flow isstopped, the print material and the (over)heated nozzle then come toequilibrium, which causes the print material to approach the nozzletemperature in the current art. This degrades the print material, makingit brittle and thereby causing clogging. In certain of the disclosedembodiments, the providing of ‘slow’ and ‘fast,’ such as zoned, heatingallows for the use of the ‘slow’ mode to maintain the nozzle innertemperature below the degradation temperature of the print material, anduse of the ‘fast’ mode may be used only at flow condition. Thus, whenthe print material flow stops in the disclosed embodiments, the ‘fast’mode may be turned off quickly, thus preventing a temperature rise abovedegradation temperature.

FIG. 1 is a block diagram illustrating an exemplary FDM printer 100. Inthe illustration, the FDM printer 100 includes an X-Y axis driver 102suitable to move the print head 104, and thus the print nozzle 106, in atwo dimensional plane, i.e., along the X and Y axes. Further included inthe FDM printer 100 for additive manufacturing are the aforementionedprint head 104 and print nozzle 106. As is evident from FIG. 1 ,printing may occur upon the flow of heated print material outwardly fromthe nozzle 106 along a Z axis with respect to the X-Y planar movement ofthe X-Y driver 102. Thereby, layers of printed material 110 may beprovided from the nozzle 106 onto a build plate 111 along a pathdictated by the X-Y driver 102.

FIG. 2 illustrates with greater particularity a print head 104 andnozzle 106 system for an additive manufacturing device, such as a FDMprinter. As illustrated, the print material 110 is extruded via theprint head 104 from a spool of print material 110 a into and through thenozzle 106. As the nozzle 106 heats the print material 110, the printmaterial 110 is at least partially liquefied for output from an end port106 a of the nozzle 106 at a point distal from the print head 104.Thereby, the extruded print material 110 is “printed” outwardly from theport 106 a via the Z axis along a X-Y planar path determined by the X-Ydriver 102 (see FIG. 1 ) connectively associated with the print head104.

FIG. 3 illustrates an exemplary nozzle 106. The nozzle 106 may be, forexample, constituted of steel, ceramic, glass, or of any other suitablematerial to achieve the desired thermal properties. For example, a glassnozzle may reduce local thermal capacity. For example, Cp*rho*V forglass=0.75*2.2*0.05=0.0825 J/C, but for steel, the same calculationyields 0.46*7.8*0.05=0.1794 J/C, which represents more than twice thejoules needed, for heating or cooling, for a steel nozzle per degreeCelsius as is needed by the glass nozzle.

For heating of the nozzle 106, the nozzle 106 may be wrapped in one ormore wire windings 204. The nozzle 106 may additionally include one ormore sheaths 202 about nozzle 106. The nozzle 106 may also include anadditional layer or multiple layers between the wire winding 204 and thenozzle 106 outer diameter, and/or between the sheath 202 (where present)and the windings 204, such as in order to enhance thermal coupling,redistribute heat, insulate from overheating, or the like.

The sheath 202 may about the nozzle 106 as referenced, and may be over,underneath, or have embedded therein wire windings 204. The sheath 202may be press fit, plasma vapor deposited or plated, rolled foil, or thelike in its application to the shank of the nozzle 106. In theillustration of FIG. 3 and by way of non-limiting example, the sheath202 encompasses the one or more coils 204.

By way of non-limiting example, the nozzle 106 may comprise a shank 106b and port tip 106 a, comprised of steel, having at least partiallythereabout the one or more wire windings 204, such as nichrome wirewindings wrapped thereabout, wherein the windings 204 may be at leastpartially enclosed within sheath 202. The wire winding 204 may serve asa heating coil to heat the print material 110 within the inner diameterof the nozzle 106. Of note, the delivery of heat by the heating coil 204may change the resistance of the heating coil 204. Accordingly, theresistance change in the heating coil 204 maybe sensed in order toassess the level of heating being delivered to the nozzle 106. Further,the sheath 202 may be employed to refocus the heat from coil 204 backinto nozzle 106.

The coil 204 and/or multiple coil aspects or coils, and the proximity ofthose coils 204 to the nozzle 106 such as in conjunction with the smallthermal mass of sheath 202, may allow for highly refined and targetedcontrol of heat delivered to the print material printed through thenozzle 106. This may allow for expedited heating and cooling, such asnear-immediate heat up and cool down/shut off, which provides thepushing of much more significant an amount of print material 110 throughthe nozzle port 106 a than can be pushed in the known art.

More specifically, the speed and amount of print material 110 exitingthe hot end of the nozzle 106 at port 106 a may be determined by avariety of factors. Such factors may include, by way of non-limitingexample, the material printed, the extrusion rate, the rate of motion ofthe X-Y driver, and the heat applied to the extrusion material. Thelatter factor, i.e., the heat applied to the extrusion material, may beselectively employed in certain of the embodiments, such as usingwindings 204, in order to obtain substantially optimal and efficientprinting in light of others of the aforementioned print factors.

FIGS. 4A and 4B illustrate the comparison of a prior art nozzle (shownin FIG. 4A) to an exemplary resistive hot end 302 according to theembodiments, such as may be comprised of the nozzle 106, windings 204,and/or sheath 202 as shown in FIG. 4B. More particularly, the comparisonof FIG. 4 is illustrative of the differences, such as the significantdifference in thermal mass, between the prior art heating block 310 ofFIG. 4A, and the combination of the sheath 202 and windings 204 of thehot end 302 of FIG. 4B.

As shown in FIG. 4A, the current art includes a large heating block 310which integrates a heating cartridge 320 and a thermocouple 322, each ofwhich are plugged into the heating block 320. Upon actuation ofthermocouple 322, the heating block 310 begins to heat, and passes theheat through the heating block 310 to the so-called “hot end” of thenozzle, which in turn heats the print material 110 within that portionof the nozzle 330 receiving the delivered heat just above the distal tipof the nozzle 330. As shown, the nozzle 330 threads into or otherwiseconnectively integrates with the heating block 310.

In sum, the foregoing forms a “hot end” having a significant thermalmass in the known art. This thermal mass corresponds to a characteristicthermal momentum, which carries with it a particular heating and coolingramp rate. Because of this ramp rate, the heating block of the known artcan neither be turned on nor off quickly and efficiently, therebycausing bumps and nipples in the printed material path, as well asnozzle bleeding and clogging.

In stark contrast to the known art and as illustrated in FIG. 4B, thethermal mass of the disclosed embodiments for hot end 302 issignificantly reduced over the thermal mass provided by the known art.Accordingly, the disclosed embodiments of the hot end 302 heat moreexpediently than the known art, and cool more expediently than the knownart. That is, the minimal thermal capacity provided by certain of thedisclosed embodiments of the hot end 302 provides a lower temperaturecapacity than the known art, and consequently is appreciably moreresponsive to application of or removal of energy to the hot end 302.

In certain of the embodiments and in order to optimize the foregoinglower temperature capacity over the known art, the winding or windings204 may vary by type, length, and/or actuation timing and manner inaccordance with the location of the windings 204 along the geometry ofthe hot end 302. For example, high density windings may be put at thenozzle taper approaching the port 106 a in order to provide maximum heatand maximum heating control at the exit port 106 a for the printmaterial.

Additionally, although the example illustrated in FIG. 4B may include aheating block, such as in the form of sheath 202, which may include athermocouple, the skilled artisan will appreciate that such a heatingblock may or may not be present with the heating methodologies providedthroughout, by way of non-limiting example. That is, windings 204 mayreside directly on nozzle 106, such as being wet wound thereon, may haveone or more layers between windings 204 and nozzle 106. In addition, thewindings 204 may or may not be surrounded by sheath 202.

The embodiment illustrated in FIG. 4B and other like embodiments maythus allow for faster ramping of heat application to the extruded printmaterial, and may allow for shutoff of extrusion of the print materialat a notably faster rate, than in the known art. This is due, in part,to the refined control provided by the wire winding 204 about thenozzle, and the improved thermal coupling thus provided between the heatavailable from the wire winding 204 and the print material 110 withinthe nozzle 106. It should be noted that thermal mass concerns may alsobe addressed by control software, and, in an exemplary embodiment, aservo drive, such as a 2.5 kHz servo drive, that at least partiallyprovides energy to the wire winding 204.

Different power formats may be employed to provide heating energy to thewire winding 204 in certain of the embodiments. For example, asillustrated in FIG. 5 , certain power sources 350 may be matched withparticularity to certain types of wire windings 204, certain types ofnozzles 106, and so on. By way of example, Newtonian heating, i.e.,providing current to the wire winding to generate heat, may be performedin conjunction with any of various types of nozzles and/or with varioustypes of wire windings 204, such as the wire windings 204 embedded insheath 202 of FIG. 5 . Other energy types 350 may be employed to providethermal excitation to the wire windings 204, such as irradiation, radiofrequency excitation, ultrasonics, microwaves, or any other powerprovision techniques understood to the skilled artisan. Moreover and asreferenced above, certain types of power sources 350 may be specificallymatched to certain types of wire windings 204 and nozzles 106, such aswherein infrared excitation may be employed with a glass nozzle forimproved thermal coupling and ramp time, or such as wherein the wirewinding comprises a bulk element rather than individual windings.

In additional alternative and exemplary embodiments, such as thatillustrated in FIG. 6 , a distinct wire winding may not be provided aswire winding 204, but rather distinct characteristics may be providedaround or embedded in nozzle 106 to serve effectively as windings 204,as that term is used herein. By way of example, the sheath 202 may beprovided about the nozzle 106 to provide thermal coupling to aparticular heating source, such as to receive microwave energy forheating. That is, the sheath 202 may be embedded or otherwise formedwith characteristic materials that are thermally excited by bombardmentusing microwaves, which will thereby allow the sheath 202 to impart heatdirectly to the nozzle 106.

Of course, the wire windings or like heating elements 204, rather thanbeing wound onto or otherwise directly applied to nozzle 106, may residewithin sheath 202 separate and apart from nozzle 106. The providing ofthe sheath 202 as a secondary physical element from nozzle 106 but as aprimary thermal coupling thereto allows for fitting of the thermalcoupling element onto a nozzle 106 after creation of the nozzle 106,i.e., sheath 202 having therein windings 204 or the equivalent thereofmay be provided as a “bolt on,” post-manufacture component to the nozzle106.

By way of non-limiting example, the windings 204 may take the form ofbulk element 204, as shown in FIG. 6 . This bulk element may be subjectto structure 606 that is also embedded within sheath 202, such as tomaintain the bulk element 204 at a given distance from nozzle 106 so asto maintain a certain level of heating. Moreover, sheath 202 mayinclude, for example, an embedded reflective cavity 608, such as toredirect heat from element 204 back toward nozzle 106 for optimizedheating.

FIG. 7 illustrates with particularity an exemplary nozzle 106 having athermal coupling element 402. In the illustration, the thermal couplingelement 402 is included in a sheath 202, and also includes, embeddedtherein, a resistive wire wrapping 204. As such, an electric current maybe “plugged into” sheath 202 to resistively and thermally excite thesheath 202, thereby causing element 402 to heat the print material 110within the nozzle 106 at locations adjacent to the element 402.

More particularly, the windings 204, or the equivalent thereof forreceiving energy and thermally coupling to deliver heat to the nozzle106, may thus be provided on the nozzle 106, in a ring/sheath around thenozzle 106, or at both positions, by way of non-limiting example, suchas to provide convection, conduction, and/or radiative heating focusedon the nozzle 106 and the printing material 110 therein. By way ofexample, wire winding 204 may be of nichrome resistance wire asmentioned above, and may use ceramic (silicate) adhesive. Moreover andas referenced herein, various insulators, such as glass fabric, may beincluded on-board the nozzle as a shield from the winding 204 or sheath202, or as a shield between the winding 204 and the sheath 202, orbetween the winding 204 or sheath 202 and the external environment. Suchinsulators may also include reflectors, by way of non-limiting example,and may thus be used on the inner diameter of the sheath 202 to redirectheat back toward nozzle 106. By way of particular example, an exteriorsurface or surfaces, either integrated on-nozzle or as a separatesheath, may be highly-reflective such that, for IR power is produced atthe nozzle 106, that IR power that would otherwise be lost is redirectedback into the nozzle 106 by the insulating layer.

By way of further example, a direct-wind onto the nozzle 106 of a coil204, such as of nichrome wire, may be solidified with the aforementionedsilicate adhesive, whether or not further structurally supported byplacement of a surrounding sheath 202. Moreover, multiple layers may bewound onto the nozzle to form windings 204, and may be separated by athin layer of glass fabric, which may also provide additional strengthand stability. Yet further, matrix material around the heating elements204, whether or not heating elements 204 are embedded in a sheath 202,such as the silicate adhesive above, may be colored, such as with black,to increase emissivity, thereby increasing IR emission power. Of note,although a fast heating method, IR generally has little heatingcapacity, and hence may be best used to provide modulation of flowunless enhanced in the manners discussed herein, i.e., using increasedemissivity and/or physical separation from the nozzle inner diameter toallow maximum IR power delivery.

In embodiments, the length of the sheath 202 may be varied, as may bethe relative length of the nozzle 106. Variations in nozzle length mayaccommodate different elements 402, such as to allow for differentelements 402 to serve different purposes, such to allow for the mostefficient heating of particular print materials. By way of non-limitingexample, a nozzle 106 in the embodiments may be longer than in the knownart, and may include a particular taper at the nozzle tip 106 a, such asto enhance the heating properties of heating elements 402 that may beemployed, particularly such as to improve the temperature gradientprovided by the element 402 to the nozzle 106 to correspondingly enhancethe maximum feed rate of the particular print material 110 in the nozzle106.

As was mentioned above in relation to measuring heat delivered based onresistance (or other electrical characteristic) change in winding 204,the characteristics of element 402, such as the resistance orconductance thereof, may be readily sensed in order to assess the heatbeing delivered to nozzle 106. More particularly, element 402 and/orsheath 202 may be provided with sensors 520 that are embedded in orotherwise associated with sheath 202. The data related to changes in,for example, the resistance or conductance of sheath 202 may then bedirectly or indirectly indicative of the temperature of the element 402at the measured point or points, thereby allowing for very precisetemperature sensing and control at the nozzle tip 106 a.

More particularly, a sensor 520 may be embedded in or on, or otherwisephysically associated with, a sheath 202 placed around a print nozzle106. The sheath 202 may include therewithin a heating coil 204. Thus,the sensor 520 may receive, directly or indirectly, a heat reading ofthe heat delivered by the heating coil 204 to nozzle 106. In addition tosensor 520 as shown, the sensor may comprise embedded traces or otherinter- or intra-connective elements, as will be understood to theskilled artisan.

In additional and alternative embodiments, a thermocouple (not shown)may also be included in the sheath 202 provided around the nozzle 106,as may be one or more expedited cooling mechanisms. For example, FIG. 7illustrates, by way of non-limiting example, a cooling tube 530, whereina small amount of air (or another gas) forced into the tube 530 or beingvented from the tube 530 may increase or decrease the rate of which heatdelivered to the nozzle 106. The cooling tube 530 may include one ormore valves (not shown) to allow for limitations on air or other gasesreleased or received. Moreover, other cooling methodologies may beemployed using the tube 530. By way of example, inlet and outlet tubesmaybe provided to enable a closed looped cooling system, such as whereincooling liquid or gas, such as water or air, may be circulated into onetube and out of the other.

Experientially, a 4-up 0.065 mm nichrome wire winding with L˜=70 mmgives ˜21.6 ohms and an 0.3 ohm swing over a 250 C swing in 3 mm PLAinside of a 7 mmOD/3 mmID glass tube, with a resistance per temperaturegain of 0.00115 ohms/C. Higher gain may be achieved by increasing thenominal coil resistance, although that also requires higher voltage.Accordingly, in the embodiments, temperature may be discerned based onamperage—that is, temperature measurement of the coil may be trackedbased on coil resistance. Of course, on-board thermocouples, RTDs, orother contact-sensing technologies, and/or optical sensing technologies,to assess heating may be employed as sensor(s) 520 in embodiments.

FIG. 8 illustrates that nozzle 106 heating may be provided in one orseveral “zones” or “phases”. For example, provided may be a firstheating zone 702 for heating the length of the print material melt 110within nozzle 106; a second heating zone 704 for “high speed” melts,such as may necessitate added power for taller melts; and a thirdheating zone 706 specifically for the nozzle tip 106 a, at which pointthe highest power density is needed for the melt exiting port 106 a intothe pattern. Moreover, the zones 702, 704, 706 may be provided byproviding overlapping windings 204 a, 204 b, 204 c, and/or by providingone or more concentric or staggered sheaths 202 a, 202 b, 202 c thateach include discrete windings. Alternatively, one or more staggered orconcentric sheaths may be provided over multiple overlapped zonewindings, i.e., the layers may comprise winding 1, winding 2, thensheath 1; or may be concentrically provided successively over eachwinding, i.e., the layers may comprise winding 1, sheath 1, winding 2,sheath 2, etc.

In short, multiple zones of coils with differing power densities allowsfor the presentation of different levels of power to different areas ofthe melt. Of note, the multiple resistors of the multiple coil zones mayshare one common leg, thus reducing the number of wires coming off theheater.

As discussed throughout, for optimal control and power expenditureimpact, it may be desirable to use direct resistive heating (andcooling) as close as is practicable to the print material within thenozzle. Accordingly, the heating element may be a winding, a sheetmaterial or bulk material (collectively “winding” throughout, unlessotherwise indicated) highly adjacent to the print material within thenozzle.

The heating elements discussed throughout may be included as separateheating elements, or as part of a sheath 202 to be fitted over thenozzle 106. In such instances, the heat provided may be conductive(i.e., Newtonian), convective, or radiative (i.e.,Planck/Stefan-Bolzmann). Additionally, a thermocouple to provide therequisite heating energy may be wet-wound with the coil structure, byway of non-limiting example. Further, the sheath(s) may be replaced insuch embodiments without need to replace the nozzle 106.

In the foregoing detailed description, it may be that various featuresare grouped together in individual embodiments for the purpose ofbrevity in the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that any subsequently claimedembodiments require more features than are expressly recited.

Further, the descriptions of the disclosure are provided to enable anyperson skilled in the art to make or use the disclosed embodiments.Various modifications to the disclosure will be readily apparent tothose skilled in the art, and the generic principles defined herein maybe applied to other variations without departing from the spirit orscope of the disclosure. Thus, the disclosure is not intended to belimited to the examples and designs described herein, but rather is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a first inner diameter and a first outer diameter and a sheath body therebetween, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil at least partially contacting the first inner diameter of the at least one sheath and fully embedded in the sheath body; and at least one energy receiver associated with the at least one wire coil, wherein the at least one wire coil comprises a first wire coil and a second wire coil capable of correspondingly providing a first temperature zone and a second temperature zone.
 2. The heating element of claim 1, wherein the first and second wire coils are at least partially staggered along a longitudinal axis of the 3D printer nozzle.
 3. The heating element of claim 2, wherein the first and second wire coils are at least partially staggered along a longitudinal axis of the 3D printer nozzle.
 4. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a first inner diameter and a first outer diameter and a body therebetween, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil at least partially contacting the first inner diameter and fully embedded within the body of the at least one sheath, the at least one wire coil providing two distinct temperature zones according to a varying coil density of the at least one wire coil; and at least one energy receiver associated with the at least one wire coil, wherein the energy receiver comprises at least one of a Newtonian, a convective, and a radiative energy receiver.
 5. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a first inner diameter and a first outer diameter and a solid body therebetween, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil having a variable coil density to provide two heating zones, at least partially contacting the first inner diameter of the at least one sheath, and fully embedded in the solid body thereof; and at least one energy receiver associated with the at least one wire coil, wherein the at least one sheath shares a thermal mass with the 3D printer nozzle.
 6. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a first inner diameter and a first outer diameter and a sheath body therebetween, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil at least partially contacting the first inner diameter of the at least one sheath, being fully embedded within the sheath body, and having a varying coil density capable of providing at least two distinct heating zones; and at least one energy receiver associated with the at least one wire coil, wherein the at least one energy receiver comprises a thermocouple.
 7. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a sheath body bounded by a first inner diameter and a first outer diameter, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil fully embedded in the sheath body, at least partially contacting the first inner diameter of the at least one sheath, and having a variable coil density such that two different temperature zones are thereby provided; and at least one energy receiver associated with the at least one wire coil, wherein the variable coil density of the at least one wire coil comprises a high density winding at a taper portion of the 3D printer nozzle and a lower density winding along a non-taper portion of the 3d printer nozzle.
 8. A heating element for a 3D printer nozzle, comprising: at least one sheath comprising a first inner diameter and a first outer diameter, the at least one sheath sized to removably engage around an outer circumference of the 3D printer nozzle; at least one wire coil at least partially contacting the first inner diameter of the at least one sheath and fully embedded in a body of the sheath bounded by the first inner diameter and the first outer diameter, wherein the at least one wire coil has a varying coil density to provide two distinct heating zones; and at least one energy receiver associated with the at least one wire coil, wherein the at least one wire coil comprises a wet winding. 